1. Field of the Invention
The present invention relates generally to a process for recovering metals from an aqueous metal-bearing solution and, more particularly, to a process which utilizes metalloproteins immobilized on an insoluble support to remove metal ions such as the main group, transition, lanthanide, and actinide ions from the aqueous metal-ion bearing solution.
2. Description of the Prior Art
Vast quantities of metal-contaminated water are generated annually in the industrial world. Additionally, a tremendous amount of metal-contaminated water from past industrial activities exists. These solutions, which are generated as a by-product or direct result of both conventional non-nuclear and nuclear processes, often contain a variety of metals which makes selective recovery difficult and uneconomical.
Presently-known methods for removing metals from aqueous wastewater streams involve techniques which are sometimes ineffective or expensive when low concentrations of metal ions (1-100 mg/L) are involved. Methods known and utilized today are referred to in the art as chemical precipitation, ion-exchange, solvent extraction, electrochemical treatment, reverse osmosis and membrane technology methods.
A presently-known method which has presented an alternative to other known methods and shows some promise for removing low concentrations of metals from aqueous wastewater streams utilizes immobilized non-living biomass. With this method, procaryotic and eucaryotic cells are employed since they are capable of binding metal ions as a precursor to removing a metal of interest from the wastewater stream. This biomass method utilizes biomass components such as cell wall components, polysaccharides and cellular proteins. Since these materials bind metal ions for a variety of purposes in living organisms, they give dead biomass an appreciable ability to bind metal ions in a process for removing metal from an aqueous wastewater stream.
Each of the individual metal-binding components of biomass inherently has its own selectivity and affinity for metal ions. However, while some overall degree of selectivity and specificity for individual metal ions is possible with this process, the biomass material, because of its complex composition, has limitations in its degree of specificity. This lack of specificity causes each of the biomass components to adsorb multiple metal ions from a solution. Since each of the biomass components utilized adsorbs ions of more than one metal suspended in the wastewater stream, it is difficult to concentrate individual metal ions of interest from multiple metal ion-bearing solutions.
As seen from the foregoing, all presently-known processes for recovering metals from aqueous wastewater streams have their shortcomings. Therefore, there is a need for an improved process for removing metals and, more particularly, a selected metal of interest, from aqueous wastewater streams which overcomes both the inefficiency and metal selectivity problems associated with these known processes.